It was Hnaflbaflsniflwhifltafl an early form of Thud mentioned in Going Postal

‘This, my lord,’ said Gilt, gesturing to the little side table on which had been set the rough-hewnpiece of stone. ‘Is this not an original Hnaflbaflsniflwhifltafl slab? Llamedos bluestone, isn’t it?And the pieces look like basalt, which is the very devil to carve. A valuable antique, I think.’